Fastening device for psa abrasive disc

ABSTRACT

A backup pad having a protruding centering button to quickly fasten pressure sensitive adhesive abrasive discs and other surface treating discs on a backup pad for a conventional power rotary tool.

United States Patent 1191 Dosser [73] Assignee: Minnesota Mining andManufacturing Company, St. Paul, Minn.

22 Filed: Feb. 11, 1974 211 App]. No.2 441,262

1451 May 20, 1975 2,767,527 10/1956 Tocci-Guilbert 51/379 2958,161611/1960 Foland 2.991.596 7/1961 Walters 51/376 Primary Examiner-OthellM. Simpson Alzorney, Agent, or FirmA1exander, Sell, Steldt & DeLaHuntABSTRACT A backup pad having a protruding centering button to 52 US. Cl.51/376 51 1111. C1. B24d 17/00 qulckly fasten PresSure Sensmve adhesweabraswe [58] Field 61 Search 51/358, 376, 378, 389 discs and otherSurface treating discs on a backup pad for a conventional power rotarytool.

[56] References Cited UNITED STATES PATENTS 9 Claims, 4 Drawing Figures2,666,281 1/1954 Tocci-Guilbert 51 379 4 1 Q 1 /0 /4A 111 1 1 1 1 111/4a 1, wfla FASTENING DEVICE FOR PSA ABRASIVE DISC BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to a backuppad and pressure sensitive adhesive (PSA) coated surfacing disc, and inone aspect, to a disc fastening member on a backup pad for aconventional rotary power tool.

2. Description of the Prior Art Coated abrasive discs, which haveexisted for decades in a wide spectrum of constructions, can be used toremove stock, cut grooves, polish a surface, etc. These discs aretypically and preferably constructed so that the disc can be mounted anddemounted with a minimum of effort. That this had been an object of manyinventions is evidenced by the number of patents directed to quickchange tools. To the best of our knowledge and belief, however, alltools heretofore known have suffered from one or more of suchdisadvantages as high cost of fabrication, excessively complicatedmechanism, danger of damaging either the disc or the drive assemblyduring installation or removal, necessity for separable fasteners ofwhich one tends to lose a part, special mounting tools, inability toresist the torque encountered in normal use, tendency to mar theworkpiece, etc.

One means of quickly mounting a disc is by the use of a pressuresensitive adhesive (PSA) coating on the backside of the disc; there isan advantage of a quick change but this advantage is offset by thehazard of a disc flying off during normal speed operations. This isparticularly true if the PSA disc is not centered on the backup pad. Theknown prior art has not provided any fastener or centering member to aidin securing the PSA disc to the backup pad.

SUMMARY OF THE INVENTION The present invention provides an improvedfastening device for quickly attaching a pressure sensitive adhesive(PSA) coated abrasive disc to a backup pad for a rotary power tool. Thepresent invention eliminates the need for tools and other separatepieces to aid in placement or attachment of the discs to the pad.

The present invention includes a conventional backup pad comprising acircular backup plate and a central fitting. The backup pad is providedwith a centering button which is secured to and protrudes from the discsupporting surface of the backup plate.

The centering button aids in centering the disc on the backup plate andalso aids in preventing hazardous lat eral displacement of the PSA discrelative to the backup plate when rotating at high rpms. The novelbackup pad device provides quick attachment and fail-safe retention ofpressure sensitive adhesive coated abrasive discs and other PSA coatedsurfacing discs that are used on power tools that may operate at speedsof 4,000 to 5,000 rpms.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fullyunderstood by reading the following detailed description which refers tothe accompanying drawing, in which like reference numbers refer to likeparts in the several views, and in which:

FIG. l is an exploded side elevational view of the backup pad and a PSAabrasive disc, constructed according to the invention.

FIG. 2 is a plane view of the assembly of FIG. 1 with portions cut awayto show hidden portions.

FIG. 3 is a vertical section taken generally on the line 3-3 of FIG. 2;and

FIG. 4 is a vertical cross-sectional partial view of a modification ofthe backup pad of FIGS. 1 to 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to thedrawing there is illustrated in FIG. 1 a generally circular backup padgenerally designated 10 and an abrasive disc 13 embodying the invention.The backup pad 10 includes a nylon disc-centering but ton 11 having aregular geometric shape and comprising a short neck 11a protrudingoutward from a disc supporting surface 14a of the pad and terminatingwith a shoulder 11b formed about the outer protruding end of the button11. The button 11 provides for the firm engagement and the centering ofthe abrasive disc 13 on the backup pad.

Backup pad 10 further includes a backup plate 14 having a discsupporting surface 140 and a rear side 14b. The backup plate 14 has acentral fitting in part provided by a threaded metal shaft-connectinghub 15 and in part by a threaded base 112 of the button 11 as seen inFIG. 3.

The shaft-connecting hub 15 is an insert permanently affixed in anopening 140 in the backup plate 14. The button base Us is permanentlyaffixed in the opening 140 coaxially with the hub 15.

The button 11 protrudes from the supporting surface 14a in a manner suchthat an opening 13f in the abrasive disc 13 is easily snapped over theshoulder 11!; to fit around the neck 11a. In the illustratedembodiments, the button 11 and the opening 13f are circular but theycould be triangular, square, star-shaped, or have other selectedgeometric shapes. Preferably the button 11, and especially its neck llaare continuous to provide sufficient strength to resist any tendency ofthe disc to migrate laterally. The opening 13f in the disc 13 ispreferably slightly smaller than the shoulder 11b and is slightly largerthan the adjacent portion of the neck 11a. The length of the neck 11a,as measured from the supporting surface 14a, is approximately equal tothe total thickness of the abrasive disc 13 at its opening 13f.

The abrasive disc 13 includes a granular coating 13a, a support basematerial 1312, a pressure sensitive adhesive coating 13c, and theopening 13f. The PSA coating 13c adheres the abrasive disc to the entiredisc supporting surface 14a of the backup pad 10.

As FIG. 3 illustrates, the shoulder 11b of the button 11 has a beveledouter edge He designed to temporarily expand the opening 13f in disc 13upon placement of the disc on the backup pad. An under surface 11d ofthe shoulder 11b engages the abrasive coating 13a of the abrasive disc13 adjacent to the opening 13f. For that purpose, the backing 13b of thedisc 13 is made of a flexible material such as paper or cloth so as tofacilitate the expansion of the opening 13f.

In FIG. 4, the backup pad has a central fitting which is provided by aninternally threaded metal shaftconnecting hub which is permanentlyaffixed to a backup plate 114. The hub 115 is inserted into a centralopening 1140 in the backup plate 114 and swaged around a metal washer119.

The centering button 111 is a separate metal piece which is alsointernally threaded for attachment to a driving shaft 120 of a rotarypower tool (not shown). The centering button 111 includes a neck 111aand a shoulder lllb which is formed with a beveled outer edge 111c. Anunder surface 111d of the shoulder 11 1b engages the abrasive coating113a of the abrasive disc 113 adjacent to its opening 113f.

The backup plate 114 includes a depression 114d around the centralfitting. This permits the centering button 111 to be replaced by ashorter button which would be recessed with respect to the planeof theworking surface of the abrasive disc 113, thus providing a wider workingband and less likelihood that the button will contact a work piece.

If desired, the backup pad may include two or more centering buttons asdescribed, preferably symmetrically arranged about the central fitting.

Backup plates may be formed of a variety of materials, such as multi-plyphenolic cloth laminate or polycarbonate. If a rigid material is used,the disc supporting surface may be a layer of an elastomeric material.By using a rigid material, the circular backup plate, the centralfitting and the centering button may be formed as a single piece ofmaterial.

I claim:

1. In combination, a rotary backup pad and a pressure sensitive adhesiveabrasive disc having a centering opening of a regular geometric shape,said backup pad designed for supporting and readily removably retainingsaid disc, said backup pad comprising a circular backup plate having adisc supporting surface;

a central fitting adapted to connect to a rotary driving shaft of apower driven tool;

a centering button which protrudes from the disc supporting surface,which button is formed at its protruding end with a shoulder which isslightly larger than the opening of the disc and with a neck 3. Acombination of claim 1 wherein the circular backup plate, the centralfitting and the centering button are formed as a single piece ofmaterial.

4. A combination of claim 1 wherein the disc supporting surface of thebackup plate is covered with a resilient surfacing adapted to aid inreceiving and holding the pressure sensitive adhesive coated abrasivedisc thereon.

5. A combination of claim 1 wherein the shoulder of said centeringbutton has an under surface spaced from and opposed to said supportingsurface to engage the abrasive surface of a said abrasive disc adjacentto the opening in the abrasive disc.

6. A combination of claim 1 wherein a centering button is located at thecenter of the backup pad and is internally threaded to provide at leasta part of the central fitting.

7. A combination of claim 1 wherein the centering button is an integralpart of the backup plate.

8. The combination of claim 1 wherein the central fitting is provided byan internally threaded metal hub permanently affixed to the backupplate, and the centering button is a separate metal piece which isinternally threaded for attachment to the driving shaft of the powertool, and the backup plate is depressed around the central fitting.

9. The combination of claim 7 wherein the centering button, when thebackup pad and abrasive disc are attached to the power tool, does notsubstantially project beyond the plane of the outer working portion ofthe which is equal to or slightly smaller than the open- 40 abrasivesurface.

ing of the disc and has a length equal to or greater

1. In combination, a rotary backup pad and a pressure sensitive adhesiveabrasive disc having a centering opening of a regular geometric shape,said backup pad designed for supporting and readily removably retainingsaid disc, said backup pad comprising a circular backup plate having adisc supporting surface; a central fitting adapted to connect to arotary driving shaft of a power driven tool; a centering button whichprotrudes from the disc supporting surface, which button is formed atits protruding end with a shoulder which is slightly larger than theopening of the disc and with a neck which is equal to or slightlysmaller than the opening of the disc and has a length equal to orgreater than the thickness of the disc at its opening to center theabrasive disc on the support surface and to restrict lateraldisplacement of the abrasive disc relative to the backup pad during theoperation thereof.
 2. A combination of claim 1 wherein said centralfitting is integral with said centering button and has an inner threadedbore portion that screws onto the driving shaft of the rotary powertool.
 3. A combination of claim 1 wherein the circular backup plate, thecentral fitting and the centering button are formed as a single piece ofmaterial.
 4. A combination of claim 1 wherein the disc supportingsurface of the backup plate is covered with a resilient surfacingadapted to aid in receiving and holding the pressure sensitive adhesivecoated abrasive disc thereon.
 5. A combination of claim 1 wherein theshoulder of said centering button has an under surface spaced from andopposed to said supporting surface to engage the abrasive surface of asaid abrasive disc adjacent to the opening in the abrasive disc.
 6. Acombination of claim 1 wherein a centering button is located at thecenter of the backup pad and is internally threaded to provide at leasta part of the central fitting.
 7. A combination of claim 1 wherein thecentering button is an integral part of the backup plate.
 8. Thecombination of claim 1 wherein the central fitting is provided by aninternally threaded metal hub permanently affixed to the backup plate,and the centering button is a separate metal piece which is internallythreaded for attachment to the driving shaft of the power tool, and thebackup plate is depressed around the central fitting.
 9. The combinationof claim 7 wherein the centering button, when the backup pad andabrasive disc are attached to the power tool, does not substantiallyproject beyond the plane of the outer working portion of the abrasivesurface.